We control the quantum mechanical motion of neutral atoms in an optical lattice by driving microwave transitions between spin states whose trapping potentials are spatially offset. Control of this offset with nanometer precision allows for adjustment of the coupling strength between different motional states, analogous to an adjustable effective Lamb-Dicke factor. This is used both for efficient one-dimensional sideband cooling of individual atoms to a vibrational ground state population of 97% and to drive coherent Rabi oscillation between arbitrary pairs of vibrational states. We further show that microwaves can drive well resolved transitions between motional states in maximally offset, shallow lattices, and thus in principle allow for coherent control of long-range quantum transport.
This chapter discusses the physics of ultracold atoms trapped in optical lattices, i.e., ordered arrays of microscopic traps produced by the interference of counterpropagating laser beams. The motion of the atoms in these ‘crystals of light’ can be described in terms of a periodic potential, similar to the one experienced by the electrons of an ideal crystalline solid. The chapter focuses on the physics of quantum transport in optical lattices, which both provides a testing ground for ideal solid-state physics and constitutes an important resource for the determination of fundamental constants (e.g., the fine structure constant) and for the use of ultracold atoms as very precise sensors of forces (e.g., gravity).
This dissertation details the construction of a neutral ultracold atom system along with one completed experiment and one future experiment. This systems contains a two-stage slowing/cooling scheme with a Zeeman slower and a magneto-optical trap (MOT), as well as an in-vacuum optical cavity. The optical cavity was specially designed for precision measurement experiments. When near resonance atoms are present in the cavity, they cause a phase shift in the light. This enables use of the cavity light transmission as a minimally invasive feedback for information on the presence of atoms in the cavity. We look at this atom cavity interaction in two regimes: a deep lattice and a shallow lattice. Atoms confined to a deep optical lattice are constrained to thousands of individual wells. Any feedback on the lattice from motion of atoms in a single well is amplified by thousands due to this repetition. We exploit this deep lattice uniformity to measure atomic motion immediately after release from the deep lattice using another very shallow probe lattice. The feedback from the atomic motion on the probe lattice cavity transmission is used to measure the atomic sample’s original temperature without losing the atoms. We measure the sample's temperature in both the axial and radial direction, with the axial measurement taking
<10 mus with the ability to recapture
75 of the atoms back into the lattice. Atoms in a shallow lattice have wavefunctions spread out across multiple lattice cites. This enables them to undergo a process called Bloch oscillations, which requires a periodic potential plus a uniform force (gravity). I perform a simulation of the coupled atom and lattice distributions to optimize our experimental realization of the system. The atomic oscillations due to gravity imprint their oscillation frequency on the transmission of cavity light, which enables us to measure the force on the atoms which is directly proportional to the frequency. We plan on using this feature to perform a precision measurement on our atoms to look for ultralight dark matter. I estimate our limits on this type of dark matter, and discuss the future of this experiment.